If the WW was not RVSM compliant then wouldn't that suggest that extra fuel be taken in case higher levels were not available?
You would have thought so. Instead, the thinking may have been to be light enough to reach 390 if unable to operate at RVSM levels. We don't know this was the underlying intent during the flight planning, but this was what transpired. They requested to go above RVSM instead of below due to fuel burn, and they were capable of reaching 390 (possibly because not full fuel).
After 3 years how did this not find its way into the report?